prefer link in OSPF using multipoint FR interface

From: Koen Zeilstra (koen@koenzeilstra.com)
Date: Sun May 21 2006 - 09:15:26 ART

Hi group,

Suppose you have 3 routers.

R1 is the frame-relay hub with a multipoint sub interface. R2 and R3 are
spokes with a physical FR interface.

R2 and R3 have a shared ethernet segment.

                 R1-------(FR)-------|
                 | |
                 | |
                 (FR) |
                 | |
                 | |
                R2----(ethernet)-----R3

I want to like to prefer the path for R2 to go via R3 for routes behind
R1 instead of directly to R1.

I can use ip ospf cost on the physical interface of R2 to make the FR link
less interesting and prefer the ethernet to R3. However for traffic coming
from networks behind R1 this won't work. That traffic will still go trough
the FR link R1-R2 instead of using R1-R3-R2. I cannot set ip ospf cost on
an interface basis on R1 since that is a multipoint sub. Setting cost on a
neigbhor is also not allowed for the same reason.

Hope this is clear.

Anybody a solution for this?

thanks,

Koen

-----------------------
If little else, the brain is an educational toy.
                 -- Tom Robbins

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